TWI798995B - Grain growing method of textured ceramics - Google Patents

Abstract

A grain growing method of textured ceramics includes steps as follow. A raw material mixing step, a tape-casting step, a laminating step, a cutting step, a pressurizing step and a sintering step are performed. Therefore, textured ceramics with different grain growing orientations can be offered by a template with a single crystal orientation and by a single grain growing process and a sintering process.

Description

Crystal Growth Method for Textured Ceramics

The invention relates to a method for growing crystals of textured ceramics, in particular to a method for growing crystals of textured ceramics with adjustable crystal orientation.

Textured ceramics can be used as components such as sensors, actuators, and transformers due to their high piezoelectric coefficient and high electromechanical coupling coefficient, and are widely used in industrial control, environmental monitoring, communication, information systems, and medical equipment. field.

The conventional process for making textured ceramics is the reaction template grain growth method, which uses a ferroelectric material with a specific crystal orientation as the core, so that the ceramic material grows in the crystal orientation of the aforementioned ferroelectric material and covers the aforementioned ferroelectric material. To form textured ceramic crystals, the disadvantage of the reaction template grain growth method is that it is necessary to obtain a variety of reaction templates with different crystal orientations when making textured ceramics with different crystal orientations, and a single crystallization process and sintering In the process, only a textured ceramic structure with a single crystal orientation can be obtained. When there is a demand for textured ceramics with different crystal orientations, it is easy to cause waste of raw materials and spend a lot of time waiting for crystallization and sintering.

To sum up, it is an important development goal to develop a reaction template using a single crystallographic orientation and to produce textured ceramics with different crystallographic orientations through a single crystallization process and sintering process.

One object of the present invention is to provide a crystal growth method for textured ceramics, by adding a cutting step to the conventional reaction template grain growth method, so as to achieve the use of a reaction template with a single crystal orientation and a single crystallization process Through the process and sintering process, the target of textured ceramics with different crystal orientations can be produced.

One embodiment of the present invention provides a crystal growth method of textured ceramics, which includes a raw material mixing step, a coating step, a stacking and pressing step, a cutting step, a pressing step and a sintering step. The raw material mixing step is to mix an active material, a binder, a solvent and a reaction template to form a mixed slurry. The coating step is coating the mixed slurry on a plane to form a plane structure. The stacking and pressing step is stacking a plurality of planar structures to a stacking thickness to form a three-dimensional structure. The cutting step is to cut the three-dimensional structure in a cutting direction to form a customized structure. The pressurizing step applies pressure to the customized structure in all directions to form a compact customized structure. The sintering step is to sinter the compact customized structure at a sintering temperature to form a textured ceramic.

According to the crystal growth method of textured ceramics in the aforementioned embodiments, the active material can be a ceramic powder, the binder can be a polymer, and the solvent can be an organic solvent.

According to the crystal growth method of textured ceramics in the aforementioned embodiments, the reaction template can be a ferroelectric material.

According to the crystal growth method of textured ceramics in the aforementioned embodiments, the ferroelectric material can be a flat plate structure.

According to the crystal growth method of textured ceramics in the foregoing embodiments, the sintering temperature may be 800 ^° C to 1700 ^° C.

Another embodiment of the present invention provides a method for growing crystals of textured ceramics, which includes a raw material mixing step, a coating step, a stacking and pressing step, a cutting step, an internal electrode coating step, a stacking step, a A pressing step and a sintering step. The raw material mixing step is to mix an active material, a binder, a solvent and a reaction template to form a mixed slurry. The coating step is coating the mixed slurry on a plane to form a plane structure. The stacking and pressing step is stacking a plurality of planar structures to a stacking thickness to form a three-dimensional structure. The cutting step is to cut the three-dimensional structure in a cutting direction to form a customized structure. The internal electrode coating step is coating an internal electrode on at least one surface of the customized structure to form a customized internal electrode. The stacking step is stacking a plurality of customized internal electrodes to form a multi-layer structure. The pressing step is to apply pressure to the multi-layer structure to form a compact multi-layer structure. The sintering step is to sinter the compact multilayer structure at a sintering temperature to form a textured ceramic.

According to the crystal growth method of textured ceramics in another embodiment, the active material can be a ceramic powder, the binder can be a polymer, and the solvent can be an organic solvent.

According to the method for growing textured ceramics in another embodiment, the reaction template can be a ferroelectric material.

According to the crystal growth method of textured ceramics in another embodiment, the ferroelectric material can be a flat plate structure.

According to the crystal growth method of textured ceramics according to another embodiment above, the sintering temperature can be 800 ^° C to 1700 ^° C.

In this way, textured ceramics with different crystal orientations can be produced by using a reaction template with a single crystal orientation and through a single crystallization process and sintering process.

Several embodiments of the present invention will be described below with reference to the drawings. For the sake of clarity, many practical details are included in the following narrative. It should be understood, however, that these practical details should not be used to limit the invention. That is, in some embodiments of the present invention, these practical details are unnecessary. In addition, for the sake of simplifying the drawings, some commonly used structures and elements will be shown in a simple and schematic way in the drawings; and repeated elements may be denoted by the same reference numerals.

Please refer to Fig. 1, Fig. 2A, Fig. 2B, Fig. 2C, Fig. 2D and Fig. 2E. Fig. 1 shows the steps of the method 100 for growing textured ceramics according to an embodiment of the present invention. 2A to 2E are diagrams illustrating a crystal growth method 100 for textured ceramics in FIG. 1 . The crystal growth method 100 of textured ceramics includes step 110, step 120, step 130, step 140, step 150, and step 160. Figure 2A is a schematic diagram of step 110, Figure 2B is a schematic diagram of step 120, and Figure 2C and Figure 2D is a schematic diagram of step 130, and Figure 2E is a schematic diagram of step 140.

In FIG. 1 and FIG. 2A , step 110 is a raw material mixing step, which is to mix an active material, an adhesive, a solvent and a reaction template 211 in a mixing manner to form a mixed slurry 210 . Specifically, the aforementioned active material can be a ceramic powder, which can be (Na, K)(Nb, Sb)O ₃ or (Ba, Ca)(Zr,Ti)O ₃ , and the aforementioned binder can be a Macromolecule, which can be a substance that enhances the viscosity of the active substance during press molding, such as polyvinyl alcohol (Polyvinyl alcohol). The aforesaid solvent can be an organic solvent, which can fully dissolve and mix the ceramic body powder, template, and adhesive, such as ethanol or toluene. The reaction template 211 can be a ferroelectric material, which can be barium titanate (BaTiO ₃ ) or sodium niobate (NaNbO ₃ ), but the invention is not limited thereto.

Specifically, the mixed slurry 210 includes a reaction template 211 and a mixture 212, wherein the mixture 212 is formed by mixing the aforementioned active material, the aforementioned adhesive, and the aforementioned solvent, and macroscopically, it is a homogeneous phase.

In detail, the aforementioned mixing method can be stirred with a magnetic bar, but the present invention is not limited thereto. In particular, attention should be paid to the principle of not crushing the reaction template 211 during stirring.

In particular, in the conventional reaction template grain growth method, the crystal orientation of the textured ceramics is determined by the crystal orientation of the added reaction template, but the crystal orientation of the textured ceramics of the present invention is not simply determined by the aforementioned It depends on the crystal orientation of the reaction template, so in the present invention, the crystal orientation of the reaction template can be any crystal orientation.

In FIG. 1 and FIG. 2B , step 120 is a coating step, which is to coat the mixed slurry 210 on a plane to form a plane structure 220 . In detail, the coating step of step 120 can be a scraper forming process, which has a scraper 221 and a feed port 222, and when coating, the mixed slurry 210 is poured into and contacts a plane (without the feed port 222). label), one side of the scraper 221 is suspended on the aforementioned plane and moves along a coating direction (not shown in the figure), and forms a planar structure 220 on the aforementioned plane, and scrapes off excess mixed slurry 210 at the same time, but the present invention This is not the limit.

In detail, one side of the scraper 221 is suspended above the aforementioned plane with a height H. By moving the scraper 221 along the aforementioned coating direction, the planar structure 220 is coated on the moving path of the scraper 221, wherein the height H is the planar structure One of 220 is coated with a thickness L1.

In detail, the coating thickness L1 depends on the material properties of the coating machine, the reaction template 211 and the mixed slurry 210. Generally speaking, the coating thickness L1 can be less than 100 µm, preferably 20 µm, but The present invention is not limited thereto.

It is particularly noted that in the mixed slurry 210 that has just been mixed, the reaction templates 211 are not uniformly oriented in a specific direction, but after being coated by the doctor blade 221, the reaction templates 211 will be uniformly arranged in a horizontal direction on the planar structure 220 middle.

In FIG. 1 and FIG. 2C and FIG. 2D , step 130 is a stacking and pressing step, which involves vertically stacking a plurality of planar structures 220 to a stacking thickness L2 and then pressing to form a three-dimensional structure 230 . In detail, the aforementioned stack thickness L2 can be greater than 0 μm to any thickness.

Specifically, the stacking thickness L2 must meet the required shapes for cutting into various components, so the aforementioned stacking thickness L2 should depend on the components used for the textured ceramics in the subsequent processing process.

In detail, a weight 231 can be placed on the uppermost planar structure 220 , and the weight of the weight 231 can exert a pressure to increase the compactness among the plurality of planar structures 220 to facilitate subsequent steps.

It is particularly noted that each planar structure 220 has not been sintered, so each planar structure 220 formed by the mixed slurry 210 is not a hard solid, so the three-dimensional structure formed after pressing the plurality of planar structures 220 in step 130 230 has a thickness L3, wherein L2≧L3.

In FIG. 1 and FIG. 2E , step 140 is a cutting step, which is to cut the aforementioned three-dimensional structure 230 in a cutting direction A to form a customized structure 240 .

Specifically, the customized structure 240 has a thickness D and a width L4. Specifically, the thickness D is the thickness of the textured ceramic required by the device, and the width L4 is the width of the textured ceramic required by the device. Therefore, the thickness D and the width L4 should depend on the components used in the textured ceramics in the subsequent processing.

In detail, the aforementioned cutting direction A can be any direction, so that the customized structure 240 with a specific crystal orientation can be cut out in response to elements with different piezoelectric performance or dielectric performance requirements.

Step 150 is a pressurization step, which is to pressurize the customized structure 240 in all directions to form a compact customized structure (not shown in the figure). The structure 240 exerts pressure in all directions, but the invention is not limited thereto.

Step 160 is a sintering step, which is to sinter the aforementioned compact customized structure at a sintering temperature to form a textured ceramic (not shown). Specifically, the aforementioned sintering temperature may be 800 ^° C to 1700 ^° C.

In detail, the sintering temperature depends on different active materials and reaction templates. For example, the sintering temperature of (Ba,Ca)(Zr,Ti)O ₃ ceramic powder with BaTiO ₃ reaction template is about 1400 degrees Celsius ^o C, the sintering temperature of (Na,K)(Nb,Sb)O ₃ ceramic powder and NaNbO ₃ reaction template is about 1200 ^o C, but the present invention is not limited thereto.

In this way, the crystal growth method 100 for textured ceramics of the present invention cuts the three-dimensional structure according to the required crystal orientation before sintering after stacking and pressing, so as to achieve the use of a single crystal orientation reaction template and a single process The crystallization process is to produce textured ceramics with different crystal orientations.

Please refer to Fig. 3, Fig. 4A and Fig. 4B. Fig. 3 is a flow chart showing the steps of a crystal growth method 300 for textured ceramics according to another embodiment of the present invention, and Fig. 4A and Fig. 4B are drawn A schematic diagram of a crystal growth method 300 for textured ceramics shown in FIG. 3 is shown. The crystal growth method 300 of textured ceramics includes step 310 , step 320 , step 330 , step 340 , step 350 , step 360 , step 370 and step 380 . FIG. 4A is a schematic diagram of step 350 , and FIG. 4B is a schematic diagram of step 360 .

Step 310 is a raw material mixing step, which is to mix an active material, a binder, a solvent and a reaction template in a mixing manner to form a mixed slurry. Other details of step 310 are similar to step 110 and will not be repeated here.

Step 320 is a coating step, which is coating the aforementioned mixed slurry on a plane to form a plane structure. Other details of step 320 are similar to step 120 and will not be repeated here.

Step 330 is a stacking and pressing step, which involves vertically stacking a plurality of planar structures to a stack thickness and then pressing to form a three-dimensional structure. Other details of step 330 are similar to step 130 and will not be repeated here.

In FIG. 3 and FIG. 4A , step 340 is a cutting step, which is to cut the aforementioned three-dimensional structure in a cutting direction to form a customized structure 440 . Other details of step 340 are similar to step 140 and will not be repeated here.

Step 350 is an internal electrode coating step, which is to coat an internal electrode 441 on at least one surface of the customized structure 440 to form a customized internal electrode 450. Specifically, the internal electrode 441 can be made of silver, copper, Nickel, platinum and other metals or their mixtures, but the present invention is not limited thereto.

In FIG. 3 and FIG. 4B, step 360 is a stacking step, which is to stack a plurality of customized internal electrodes 450 to a thickness L5 to form a multi-layer structure 460. In detail, the thickness L5 is the thickness of the device. The thickness of the textured ceramics is required, so the thickness L5 should be determined by the components used in the subsequent processing of the textured ceramics.

Step 370 is a pressurization step, which applies pressure to the multi-layer structure 460 in all directions to form a compact multi-layer structure. This is the limit.

Step 380 is a sintering step, which is to sinter the aforementioned compact multilayer structure at a sintering temperature to form a textured ceramic (not shown). Specifically, the aforementioned sintering temperature may be 800 ^° C to 1700 ^° C. Other details of step 380 are similar to step 160 and will not be repeated here.

In this way, the textured ceramic crystal growth method 300 of the present invention cuts the three-dimensional structure according to the required crystal orientation before sintering after stacking and pressing, so as to achieve a reaction template using a single crystal orientation and a single process The crystallization process is to produce textured ceramics with multiple layers and different crystal orientations.

The following test examples are to test and prove that the crystal growth method of textured ceramics of the present invention can produce multi-layered textured ceramics with different crystal orientations through a single crystallization process using a reaction template with a single crystal orientation. In detail, in the following test examples, the active material used is BCTSHML ceramic powder, the BCTSHML ceramic powder is (Ba, Ca) (Ti, Sn, Hf) O ₃ , manganese dioxide (MnO ₂ ) and carbonic acid For the mixture of lithium (Li ₂ CO ₃ ), the binder used is polyvinyl alcohol, the organic solvent used is ethanol, and the reaction template material used is BaTiO ₃ .

Specifically, the production method of BCTSHML ceramic powder is briefly described as follows: barium carbonate (BaCO ₃ ), calcium carbonate (CaCO ₃ ), titanium dioxide (TiO ₂ ), tin dioxide (SnO ₂ ) and hafnium dioxide (HfO ₂ ) The powders are mixed and ground and then calcined to obtain (Ba,Ca)(Ti,Sn,Hf)O ₃ , then MnO ₂ and Li ₂ CO ₃ powders are added for mixing and grinding to obtain BCTSHML ceramic powder .

Specifically, the production method of the BaTiO ₃ reaction template is briefly described as follows: After grinding and mixing bismuth trioxide (Bi ₂ O ₃ ) and TiO ₂ , they are synthesized by molten salt method with sodium chloride (NaCl) and calcined to obtain Bismuth titanate (Bi ₄ Ti ₃ O ₁₂ ), and after mixing Bi ₄ Ti ₃ O ₁₂ with TiO ₂ and BaCO ₃ , the reaction template of BaTiO ₃ was synthesized by molten salt method. The aforementioned molten salt method is a chemical synthesis method, which uses salts with low melting points as the reaction medium, so that chemical reactions can be carried out in a lower temperature environment. The molten salt method is a commonly used synthetic method in the field of chemical synthesis. , so its details will not be repeated here, and the reaction templates that can be used in the present invention are not limited to this synthesis method.

Subsequently, the reaction template of BCTSHML ceramic powder and BaTiO ₃ is used for the production of textured ceramics by the crystal growth method of textured ceramics of the present invention, and is cut in different angles of cutting directions during the cutting step and sintered In the step, sintering was carried out at a sintering temperature of 1350 ^o C to obtain Test Example 1, Test Example 2, and Test Example 3, and then X-ray diffractometer (XRD) was used to determine the crystal structure of each test example , to verify that the crystal growth method of textured ceramics of the present invention can produce multilayer textured ceramics with different crystal orientations by using a reaction template with a single crystal orientation and a single crystallization process.

Please refer to Fig. 5, which is a diagram of X-ray diffraction data of various test examples of the present invention. As can be seen from Figure 5, the ceramic crystals obtained by sintering the BCTSHML ceramic powder without adding a reaction template are at (100), (110), (111), (200), (002), (210) and (211 ) and other crystal planes have obvious diffraction peak signals; Test Example 1 is a ceramic crystal obtained by cutting in a direction parallel to the BaTiO ₃ reaction template, and its crystal planes (100), (200) and (002) There are obvious diffraction peak signals; Test Example 2 is a ceramic crystal obtained by cutting the BaTiO ₃ reaction template at an angle of 45 ^o , which has Obvious diffraction peak signal; Test Example 3 is a ceramic crystal cut in the direction perpendicular to the BaTiO ₃ reaction template, which has Obvious diffraction peak signal. Based on the above results, the crystal planes of Test Example 1, Test Example 2 and Test Example 3 are different, and the crystal orientation is a vector perpendicular to the crystal plane, which means that Test Example 1, Test Example 2 and Test Example 3 have The crystal orientations are also different, showing that the crystal growth method of the textured ceramics of the present invention can effectively produce multi-layer textures with different crystal orientations by using a single crystal orientation reaction template and a single crystallization process In addition, it can also be used to manufacture components with internal electrodes to obtain various components with different electrical properties.

To sum up, the crystal growth method of textured ceramics of the present invention cuts the active material before sintering, so that it can be produced by using a reaction template with a single crystal orientation and a single crystallization process. Multi-layer textured ceramics with different crystal orientations. Compared with the conventional manufacturing process of textured ceramics with different crystal orientations, the complexity of the crystal growth method of the textured ceramics of the present invention is greatly reduced, and the process cost can also be reduced. and the waste of raw materials. In addition, it can be combined with internal electrodes to make various components with different electrical properties, so it can be widely used in various fields.

Although the present invention has been disclosed above in terms of implementation, it is not intended to limit the present invention. Anyone skilled in this art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection of the present invention The scope shall be defined by the appended patent application scope.

100,300: Crystal growth method of textured ceramics 110,120,130,140,150,160,310,320,330,340,350,360,370,380: steps 210: mixed slurry 211:Reaction template 212: Mixture 220: planar structure 221: scraper 222: feed port 230: Three-dimensional structure 231: heavy objects 240,440: Customized structures 441: inner electrode 450: Customized internal electrodes 460: multi-layer structure A: Cutting direction H: height L1: coating thickness L2: stack thickness D, L3, L5: Thickness L4: width

In order to make the above and other objects, features, advantages and embodiments of the present invention more clearly understood, the accompanying drawings are described as follows: Figure 1 is a flow chart showing the steps of a crystal growth method for textured ceramics according to an embodiment of the present invention; Fig. 2A, Fig. 2B, Fig. 2C, Fig. 2D and Fig. 2E are schematic diagrams showing the steps of the crystal growth method of textured ceramics in Fig. 1; Fig. 3 is a flow chart showing the steps of the crystal growth method of textured ceramics according to another embodiment of the present invention; Figure 4A and Figure 4B are schematic diagrams illustrating the steps of the crystal growth method for textured ceramics in Figure 3; and Fig. 5 is a diagram of X-ray diffraction data of various test examples of the present invention.

100: Crystal growth method of textured ceramics

110,120,130,140,150,160: steps

Claims (10)

A method for growing crystals of textured ceramics, comprising: a raw material mixing step of mixing an active material, an adhesive, a solvent and a reaction template to form a mixed slurry; a coating step of mixing the mixed slurry The material is coated on a plane to form a plane structure; a stacking step is to stack a plurality of plane structures to a stack thickness to form a three-dimensional structure; a cutting step is to use a cutting direction at different angles cutting the three-dimensional structure to form a customized structure; a pressing step is to press the customized structure in all directions to form a compact customized structure; and a sintering step is to sinter The temperature sinters the dense customized structure to form a textured ceramic. The crystal growth method of textured ceramics as described in Claim 1, wherein the active material is a ceramic powder, the binder is a polymer, and the solvent is an organic solvent. The crystal growth method of textured ceramics as claimed in claim 1, wherein the reaction template is a ferroelectric material. The crystal growth method of textured ceramics as claimed in claim 3, wherein the ferroelectric material is a flat plate structure. The crystal growth method of textured ceramics according to Claim 1, wherein the sintering temperature is 800°C to 1700°C. A method for growing crystals of textured ceramics, comprising: a raw material mixing step of mixing an active material, an adhesive, a solvent and a reaction template to form a mixed slurry; a coating step of mixing the mixed slurry The material is coated on a plane to form a plane structure; a stacking and pressing step is to stack a plurality of the plane structures to a stack thickness to form a three-dimensional structure; a cutting step is to cut at one of different angles Cutting the three-dimensional structure in the direction to form a customized structure; an internal electrode coating step is to coat an internal electrode on at least one surface of the customized structure to form a customized internal electrode; a stacking step , is to stack a plurality of the customized internal electrodes on each other to form a multilayer structure; a pressing step is to apply pressure to the multilayer structure in all directions to form a compact multilayer structure; and a sintering step is to The compact multilayer structure is sintered at a sintering temperature to form a textured ceramic. The crystal growth method of textured ceramics according to claim 6, wherein the active material is a ceramic powder, the binder is a polymer, and the solvent is an organic solvent. The crystal growth method of textured ceramics as claimed in claim 6, wherein the reaction template is a ferroelectric material. The crystal growth method of textured ceramics as claimed in claim 8, wherein the ferroelectric material is a flat plate structure. The crystal growth method of textured ceramics according to claim 6, wherein the sintering temperature is 800°C to 1700°C.

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